Automatic Discounts not working - 500 error

Made an order and went to checkout and got a 500 error.[17-Feb-2016 11:20:06 Australia/Sydney] PHP Fatal error: Allowed memory size of 268435456 bytes exhausted (tried to allocate 8192 bytes) in /home/tbsahprint/public_html/administrator/components/com_awocoupon/helpers/estore/hikashop/couponhandler.php on line 39

Current limit 128mb, increased to 256mb and got the following 500 error: